Cell proliferation of Paramecium tetraurelia under clinorotation.

It has been reported that Paramecium proliferates faster under microgravity in space, and slower under hypergravity (Kato et al., 2003). Effects of gravity on cell proliferation could be discussed in terms of energetics of swimming. Because of the characteristics of 'gravikinesis' as well as 'gravitaxis', Paramecium would decrease the energy expenditure under microgravity and increase it under hypergravity. The larger stock of energy would enhance the proliferation under microgravity. In order to simulate the effect of microgravity, we investigated the proliferation under clinorotation. When cells were rotated at 2.5 rpm, the proliferation rate decreased. Similar but less pronounced decrease was also found under low speed clinorotation (0.2 rpm).     

Ultrastructure and metabolic activity of pea mitochondria under clinorotation

Experimental data on the mitochondrial ultrastructure and tissue respiration in root apex as well as metabolic activity of the organelles isolated from pea seedling roots after 5-day of clinorotation are presented. It was shown that mitochondrial condensation in the distal elongation zone correlated with an increased rate of oxygen uptake on 7%. We also observed increase in rate of malate oxidation and respiratory control ratio increased simultaneously with a decreased in efficiency of oxidative phosphorylation. Such character of mitochondrial rearrangements in simulated microgravity is assumed to be a consequence of adaptation to these conditions.     

Adenilate pool and thylakoid ATP-synthase content in pea leaves under clinorotation

It is known that plant resistance to stress factors is connected with energy metabolism. The energy stored in the process of photophosphorylation in the form of ATP is used then to support respiration, transpiration, organic compound synthesis, growth and development as well as to restore cell structure after its damage under extremal environmental factors. Transformation of light energy into chemical energy of ATP is catalyzed by thylakoid membrane enzymatic complex of ATPsynthase-CF1CF0. Its activity and amount in the thylakoid membrane depends on plant growth conditions. The aim of this work was investigation of clinorotation effect on light-induced dynamics of adenyl nucleotides (AMP, ADP and ATP) and estimation of CF1CF0 content in thylakoids of pea leaves grown under slow clinorotation and vertical control.     

Microtubules spatial alterations in root cells of Brassica rapa under clinorotation

Organization of tubulin cytoskeleton in epidermis and cortex cells in different root growth zones in Brassica rapa L. 6-day-old seedlings under clinorotation has been investigated. It was shown that changes in cortical microtubules orientation occur only in the distal elongation zone. In control, cortical microtubule arrays oriented transversely to the root long axis. Whereas under clinorotation an appearance of shorter randomly organized cortical microtubules was observed. Simultaneously, a significant decrease in a cell length in the central elongation zone under clinorotation was revealed. It is suggested that the decline of anisotropic growth, typical for central elongation zone cells, is connected with cortical microtubules disorientation under clinorotation.     

Calcium balance changes in tip growing plant cells under clinorotation

Calcium is known to play an important role in the regulation of cellular processes as a secondary messenger in signal transduction to a specific response in all eucaryotic cells. Its messenger role is realized by transient changes in the Ca2+ cytosolic concentration induced by variety of external stimuli such as light, hormones and gravity. Recent findings claim the modifications in a calcium balance in plant cells in microgravity and under clinorotation reproducing partially the microgravity effect. Based on these data, the hypothesis is proposed that Ca2+ level changes can trigger the rearrangements in cell metabolism occurring in the conditions of altered gravity. However, the methods used in previous works permit only to determine the relative quantity of intracellular membrane-bound calcium and to observe the localization of free Ca2+. Therefore, it is of essential interest to measure the concentration of free calcium ions ([Ca2+]i) in plant cells under the influence of altered gravity. In this paper results from measurements of the [Ca2+]i in plant cells under clinorotation will be reviewed and discussed in an effort to examine their effectiveness, causes and consequences.     

Postural control under clinorotation in upside-down catfish, Synodontis nigriventris.

The upside-down catfish Synodontis nigriventris has a unique habit of swimming and resting upside-down in free water. This behavior leads to the assumption that the catfish has a specific gravity information processing system. We examined the postural control behaviors in the catfish under clinorotation which is usually used for producing pseudo-microgravity. Synodontis nigriventris kept its body posture at a stable area of the rotated flask in which the catfish was kept, when it was clinorotated at the rate of 60 rpm. In contrast to Synodontis nigriventris, a related species, Corydoras paleatus, did not show such steady postural control. When the flask was rotated at a lower rate of 30 rpm or a higher rate of 100 rpm, Synodontis nigriventris as well as Corydoras paleatus showed a considerable disturbed control of body posture. In this condition, they were frequently rotated with the flask. These findings suggest that Synodontis nigriventris has a high ability to keep upside-down posture and the gravity sensation in this catfish is likely to contribute to its different postural control from that of many other fishes.     

Nucleolar methyltransferase fibrillarin: Evolution of structure and functions

Fibrillarin is one of the most studied nucleolar proteins. Its main functions are methylation and processing of pre-rRNA. Fibrillarin is a highly conserved protein; however, in the course of evolution from archaea to eukaryotes, it acquired an additional N-terminal glycine and arginine-rich (GAR) domain. In this review, we discuss the evolution of fibrillarin structure and its relation to the functions of the protein in prokaryotes and eukaryotes.     

Effects of clinorotation on the structure of xylem in Arabidopsis roots]

Lignin, which is the most important component of vascular tissue, is essential material for the structural support of higher plants and considered to play a critical role in evolution of land plants. It has been postulated that development of secondary wall is mediated by gravity. However, effects of gravity on the development and the morphology of secondary cell wall have not been well investigated. In this study, effects of averaging of gravity vector using 2-D clinostat rotation on the structure of xylem was examined. The results indicated that the morphology of xylem is regulated by the orientation of gravity vector.     

Antioxidant metabolism and oxidative damage in Anthemis gilanica cell line under fast clinorotation

Plant Cell, Tissue and Organ Culture (PCTOC) - Clinostat is a device often used for applying microgravity analogs in gravitational biology studies. It can constantly change the direction of the...     

Ultrastructure of statocytes and cells of distal elongation zone of Arabidopsis thaliana under clinorotation

Results of the electron-microscopic investigation of root apices of Arabidopsis thaliana 3-, 5- and 7-days-old seedlings grown in the stationary conditions and under clinorotation are presented. It was shown the similarity in the root apex cell ultrastructure in control and under clinorotation. At the same time there were some differences in the ultrastructure of statocytes and the distal elongation zone under clinorotation. For the first time the sensitivity of ER-bodies, which are derivatives of GER and contain beta-glucosidase, to the influence of simulated microgravity was demonstrated by increased quantity and area of ER-bodies at the cell section as well as by higher variability of their form under clinorotation. A degree of these changes correlated with the duration of clinorotation. On the basis of experimental data a protective role of ER-bodies in adaptation of plants to microgravity is supposed.     

Growth and differentiation of the root cap columella and root proper under stationary conditions and in clinorotation

Results are presented from light-optical and electron-microscopy studies of the root apices of three-day-old seedlings of table beet (Beta vulgaris) grown under conditions of stationary control and in clinorotation. It is shown that the ultrastructure and topography of the organelles of the root cap statocytes (gravity-perceptive cells) and cells of the distal elongation zone (gravity-receptor cells) of the root proper clearly reflect different directions for their growth and differentiation in space and in time as a function of specialization and function. Growth and genetically determined differentiation of the cells under clinorotation conditions occur as in the control, though certain differences in their ultrastructure attest to changes in metabolism.     

Nucleolar structure during the meiotic prophase in Allium cepa anthers

Summary Naturally segregated nucleoli have been observed during the prophase in meiocytes of Allium cepa anthers. Under the light microscope the nucleolus is seen to consist of two clearly differentiated regions: a central core, which is strongly argyrophilic (ochre or dark brown) and slightly basophilic, surrounded by a basophilic peripheral region, which shows a low degree of argyrophilia. Under the electron microscope the central region appears as consisting of fibrillar elements (pars fibrosa), while the peripheral region proved to consist mainly of granules about 150 Å in diameter (pars granulosa).When the pachytene nucleolus of Allium cepa is stained with basic fuchsin, a small circular area appears intensely stained, which gradually grows larger as the pachytene proceeds. This characteristic structure, eventually reaching a size of 0.5–1.5 is regularly to be observed with a central vacuole. Under the electron microscope this area appears as a circular structure of high electron density, which corresponds in shape and size with the area revealed by the light microscope.The relationship between this new structure, which we have called globulus with other nucleolar structures is discussed.This work was partially supported by a grant from the Fondo de Ayuda a la Investigación, 1968, Spain. We wish to thank most especially Dr. M. C. Risueño, M.I. Rodriguez-García and J. M. Sogo, of the Cell Structures Section, (Department of Cytology) for their efficient collaboration. We also wish to thank M. C. Partearroyo and A. Partearroyo for technical assistance. One of the authors (J.C.S.) has a Research Training Fellowship awarded by the International Agency for Research on Cancer (World Health Organization).     

Heat shock proteins HSP70 and HSP90 in pea seedlings under clinorotation of different duration

We have previously shown an increase in the Hsp70 and Hsp90 level in pea seedlings (cv. Damir) in response to clinorotation. In this work, Western-blot analysis of the Hsp70 and Hsp90 under clinorotation of different duration--from hours to days--was carried out with pea seedlings (cv. Intensive) with more intensive seed germination and seedling growth. Under clinorotation, the higher Hsp70 and Hsp90 amounts in the germinating seeds seem to be caused by some deceleration of their hydrolysis that correlated with common slowing down of seedling growth. Time-dependent changes in response to clinorotation were determined: some temporary increase in the Hsps level with the maximum for the Hsp70 at 2 h of clinorotation and for the Hsp90--at 6 h and their subsequent returning to the control level.     

Corneal endothelial structure and function under normal and toxic conditions.

Our understanding of the function of the corneal endothelium in corneal thickness regulation, and the role of ion transport mechanisms in endothelial physiology, has expanded greatly over the past 25 years. The basic events occurring across the apical and basolateral membranes of the cells are far better understood today, although gaps still exist in the area of the relationship of the cellular and paracellular pathways and their relative contribution to the overall behavior of the endothelium. Little is known about the movement of ions or fluid between the cells or in what proportion this may occur compared to the cellular events. Furthermore, although our knowledge of the ionic movement processes has been enhanced, the link between fluid transfer across the endothelium and ion movements remains an enigma. Important questions also remain concerning the link between electrical characteristics and either ion movement or fluid transport. Improved storage solutions are needed that will preserve endothelial function after transplantation through the provision of a significant improvement in long-term cell survival. The limit to preservation time at present is about 14 days, and the use of other variables in the storage solution may extend this time. In reality, however, extension of preservation time is now of secondary importance relative to the need to enhance cell survival and reduce cell loss following surgery. Whether such improvement can be made with manipulation of the solution alone, or whether refinements are needed in the surgical technique awaits further study. Our comprehension of the biochemical linkage between energy supply and ion movement also remains uncertain in view of the particular intracellular localization of the anionic ATPases to mitochondrial loci. Despite numerous attempts there have been only a few chemicals identified that stimulate the fluid pump, but the level of stimulation has been relatively small and short-lived. No sustained effects have been found that would be of clinical benefit in reducing corneal thickness. A considerable variety of chemicals has been tested on the endothelium and it is unlikely that any new compounds will be identified that will cause enhancement of the fluid pump that would be of clinical benefit in dystrophic, or otherwise swollen, corneas. Of all the toxic responses of the endothelium the majority have been identified because of a malfunction of corneal thickness regulation, with the resultant corneal swelling, or by morphological examination. Only in a few instances has the permeability to non-electrolytes (carboxyfluorescein, inulin/dextran) been measured, and even more rarely have ion fluxes, or pump activity (3H-ouabain binding), been measured.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nucleolar structure and synthetic activity during meiotic prophase and spermiogenesis in the rat

The ultrastructure of nucleoli was examined in developing rat spermatocytes and spermatids, with the help of serial sections. In addition, the radioautographic reaction of nucleoli as examined in rats sacrificed 1 hr after intratesticular injection of 3H(5')-uridine and taken as an index of the rate of synthesis of ribosomal RNA (rRNA). Primary spermatocytes from preleptotene to zygotene have small nucleoli typically composed of fibrillar centers, a fibrillar component, and a granular component, within which are narrow interstitial spaces. During early and mid-pachytene, nucleoli enlarge to about nine times their initial size, with the fibrillar and granular components forming an extensive network of cords--a nucleolonema--within which are wide interstitial spaces. Meanwhile, there appear structures identical to the granular component but distinct from nucleoli; they are referred to as extranucleolar granular elements. Finally, from late pachytene to the first maturation division, nucleoli undergo condensation, as shown by contraction of fibrillar centers into small clumps, while fibrillar and granular components condense and segregate from each other, with a gradual decrease in interstitial spaces. In secondary spermatocytes, nucleoli are compact and rather small, while in young spermatids they are also compact and even smaller. Nucleoli disappear in elongating spermatids. In 3H-uridine radioautographs, nucleolar label is weak in young primary spermatocytes, increases progressively during early pachytene, is strong by the end of mid pachytene, but gradually decreases during late pachytene up to the first maturation division. In secondary spermatocytes and spermatids, there is no significant nucleolar label. In conclusion, rRNA synthesis by nucleoli is low in young spermatocytes. During pachytene, while nucleoli enlarge and form a lacy nucleolonema, rRNA synthesis increases gradually to a high level by the end of mid pachytene. However, during the condensation and segregation of nucleolar components occurring from late pachytene onward, the synthesis gradually decreases and disappears. The small, compact spermatids arising from the second maturation division do not synthesize rRNA.